The Effects Of Succinylcholine On The Recovery Of Atracurium-induced Neuromuscular Block

BACKGROUND: The interaction between succinylcholine and non-depolarizing muscle relaxants is quite complex, as reported in the literature, varies widely. During a rapid-sequence induction of anesthesia, succinylcholine is commonly given as an i.v. bolous to facilitate tracheal intubation, and neuromuscular blockade was maintain by injection of non-depolarizing agents. However, studies evaluating the effects of succinylcholine on the recovery of atracunum-mduced neuromuscular block are lacking. OBJECTIVES: To study the effects of succinylcholine on the recovery of atracurium-induced neuromuscular block. METHODS: The study included 40 patients (ASA I - II) who underwent elective eye surgery under general anesthesia. Anesthesia was induced with propofol, fentanyl , enflurane, succinylcholine Img/kg iv and patients were ventilated via face mask with 50% nitrous oxide in oxygen. Patients were randomly divided into two groups, tracheal intubation was performed during maximum depression (TOF=0). After tracheal intubation , whenTl (amplitude of the first twitch response of each train ) return to 75% , group 1 (n=17) received atracurium 0.5mg/kg, group 2 (n=23) received atracurium 0.5mg/kg followed by succinylcholine 1.5mg/kg ( II A ,n=13) or succinylcholine Img/ kg ( II B ,n=10)when Tl had recovered to 50% of its original baseline. The stimulation patterns used were train-of-four (TOP) to measure neuromuscular responses during anesthesia. The parameters were onset time, duration of action, 50% recovery time, 75% recovery time and neuromuscular blocking patterns. RESULTS: Tl response after atracurium-induced neuromuscular block , the duration of action , 50% recovery time and 75% recovery time , respectively , without significant differences between the two groups . Tl response after succinylcholine (1.5mg/ kg, II A) induced neuromuscular block during induction and recovery , the onset time were 0.73 + 0.26(min) vs 1.79+0.39(min), 25% recovery time were 10.21+2.99(min) vs 5.83+1.69(min) , 50% recovery time were 12.83+4.04 (min) vs 7.79+2.55(min), respectively (p<0.01), the prolonged onset timeand the short duration of action on the recovery . 75% recovery time were 16.17+5.24(min) and 16.33+7.65(min) , respectively, without significant differences. In group IIB, an intravenous dose of Img/kg succinylcholine was insufficient to cause complete neuromuscular block. CONCLUSIONS: Succinylcholine didnot prolong the recovery of atracurium and could be used safely on the recovery of atracurium-induced neuromuscular block. The prolonged onset time and the short duration of action of succinylcholine can be explained by the competitive antagonism at the receptor causing an increased amount of unbound succinylcholine . Because of the antagonistic interactions between the two drugs, increasing the doses of succinylcholine to 1.5mg/kg may be more suitable.